Behavior Of 316L Stainless Steel Research Articles

Tribocorrosion behavior of 316L stainless steel sliding against different ceramics in 0.5 M H2SO4 solution

The influence of ceramic ball wear on the tribocorrosion behavior of 316L stainless steel is little studied. This study investigated the tribocorrosion behavior of 316L stainless steel sliding against three different ceramic balls in 0.5 M H2SO4 solution. The results showed that the three ceramic balls exhibited quite different wear behaviors and the tribocorrosion behavior of 316L stainless steel was significantly influenced by the wear of the ceramic counterpart. Surface analysis indicated Si-water reactions on the Si-containing balls at high shear stress and high flash temperature. This study provides clear evidence that the selection of the counterpart materials and their wear behaviors need to be paid more attention to in tribocorrosion experimental investigations of stainless steels.

Effect of scanning speed on fatigue behavior of 316L stainless steel fabricated by laser powder bed fusion

The effect of the scanning speed on the fatigue behavior of Laser Powder Bed Fusion (LPBF)-fabricated 316L steel is investigated in this paper. To this end, fatigue limits of specimen manufactured by different scanning speeds are determined by the self-heating approach. EBSD experiments and relative density measurements are carried out to characterize the microstructure and porosity. To analyse the influence of scanning speed on the microstructure (grain morphology, texture, dislocation density and stored energy) and fatigue property, a dislocation-density, crystal plasticity and stored energy-based fatigue model is developed. The inverse optimization method is combined with EBSD experiments and uniaxial tension experiments to identify the model parameters. The experimental results show a critical scanning speed, below which the fatigue limit stays almost unchanged and decreases drastically while the scanning speed is increased beyond. Furthermore, the simulation results show that the predicted fatigue limits correspond well to the experimental fatigue ones. From experimental and numerical results, it is deduced that the critical stored energy density and maximum temperature variation are functions of the porosity and can be used to differentiate the types of fatigue: microstructure-dominated or defect-dominated. This article provides new insights which can be further used in the optimization of fatigue behavior of LPBF 316L steel with respect to the scanning speed.

Effects of Residual Stress Induced by Laser Shock Peening on Fatigue Crack Propagation Behavior in Directed Energy Deposition Stainless Steel

To investigate the effect of laser shock peening (LSP) on the fatigue crack propagation behavior of 316L stainless steel fabricated by directed energy deposition (DED), three‐dimensional finite element models of DED and compact tensile specimens before and after LSP are developed. The residual stress fields induced by DED and LSP are simulated, as well as the effects of different residual stresses on the stress intensity factor and effective stress ratio based on the contour integral method are also analyzed. The microstructure of the LSP region is observed by scanning electron microscope. When the crack length increases from 12 to 22.5 mm, the average effective stress ratio of the DED specimen is 0.133, and the average effective stress ratio of the DED specimen after LSP decreases to 0.110, which decreases by 17.3%. The fatigue lives of the DED specimen before and after LSP are 62.7% and 105.2% of that of the hot‐rolled plate. After LSP treatment, the fatigue life of the DED specimen is increased by about 1.68 times. The fracture morphology in the transient fracture zone changes from ductile and brittle mixed fracture to ductile fracture.

Fatigue behavior of 316L stainless steel fabricated via Material Extrusion Additive Manufacturing

Material Extrusion Additive Manufacturing (MEAM) is a novel technique that widens the field of additive manufacturing applications in producing metal parts. There is limited knowledge about the process-induced properties of the metal parts obtained with such a process, especially when dealing with cyclic loading. The present work aims to assess the fatigue life of 316L components fabricated via MEAM, investigating the fatigue failure mechanisms. The resulting S-N curve shows a lower fatigue limit compared to wrought 316L. Internal defects are detrimental to the fatigue life since crack initiation sites are observed from the pores resulting from the deposition strategy of the material during the printing phase.

Porosity, roughness, and passive film morphology influence the corrosion behavior of 316L stainless steel manufactured by laser powder bed fusion

The development of additively-manufactured (AM) 316L stainless steel (SS) using laser powder bed fusion (LPBF) has enabled near net shape components from a corrosion-resistant structural material. In this article, we present a multiscale study on the effects of processing parameters on the corrosion behavior of as-printed surfaces of AM 316L SS formed via LPBF. Laser power and scan speed of the LPBF process were varied across the instrument range known to produce parts with >99 % density, and the macroscale corrosion trends were interpreted via microscale and nanoscale measurements of porosity, roughness, microstructure, and chemistry. Porosity and roughness data showed that porosity φ decreased as volumetric energy density Ev increased due to a shift in the pore formation mechanism and that roughness Sq was due to melt track morphology and partially fused powder features. Cross-sectional and plan-view maps of chemistry and work function ϕs revealed an amorphous Mn-silicate phase enriched with Cr and Al that varied in both thickness and density depending on Ev. Finally, the macroscale potentiodynamic polarization experiments under full immersion in quiescent 0.6 M NaCl showed significant differences in breakdown potential Eb and metastable pitting. In general, samples with smaller φ and Sq values and larger ϕs values and homogeneity in the Mn-silicate exhibited larger Eb. The porosity and roughness effects stemmed from an increase to the overall number of initiation sites for pitting, and the oxide phase contributed to passive film breakdown by acting as a crevice former or creating a galvanic couple with the SS.

Constructing passivation film on plain carbon steel similar to that on 316L stainless steel

A high corrosion-resistant passivation film with cerium-molybdenum-chromium-nickel ions has been synthesized on plain carbon steel rebar through a chemical transformation method which significantly lowered the pitting susceptibility of the rebar in the chloride-containing concrete environment. The results indicated that the prepared film has a re-passivation self-healing property in a concrete environment with a concentration of 0.1 M NaCl, which is similar to the behavior of 316L stainless steel. The charge transfer resistance increased markedly with the extension of immersion time, reaching 3.70 × 106 Ω cm2 in about 1500 h of immersion (about 10 times of the initial Rt value). The high corrosion resistance mechanism of the film was discussed here in depth.

Experimental and constitutive modelling studies of type 316L stainless steel based on internal stress under low cycle fatigue and creep-fatigue interaction

Low cycle fatigue (LCF) and creep-fatigue interaction (CFI) behaviour of 316L stainless steel at 550 °C were investigated using experimental and modelling approaches. Results demonstrate that friction and back stress contribute to the initial hardening stage, whereas the former is primarily responsible for the subsequent softening stage. Besides, friction stress also accounts for the non-masing feature and varied softening rate. Increasing holding time induces a rise followed by a decline in friction stress, while the back stress decreases steadily to a saturated value. Moreover, a short tensile holding duration leads to planar structures and higher dislocation density. However, a longer tensile holding time promotes dislocation annihilation and subgrains growth, and elongates dislocation cells. Finally, an improved viscoplastic constitutive model was proposed based on the internal stress analysis. The kinematic hardening rule was improved by considering the cycle-dependent plastic modulus and stress relaxation, and the non-masing and variable softening rate were captured by modifying the isotropic hardening rule. In addition, holding time-related factors were also coupled into the model. The proposed model is robust for describing the cyclic features under both LCF and CFI.

Impact-sliding fretting tribocorrosion behavior of 316L stainless steel in solution with different halide concentrations

Impact-sliding caused by random vibrations between tubes and supports can affect the operation of heat exchangers. In addition, a corrosive environment can cause damage, accelerating the synergism of corrosion and wear. Therefore, the focus of this work was the impact-sliding fretting tribocorrosion behavior of 316L heat exchanger tubes at different halide concentrations. A device system incorporating the in situ electrochemical measurements of impact-sliding fretting corrosion wear was constructed, and experiments on 316L heat exchanger tubes in sodium chloride (NaCl) solution with different concentrations (0.0, 0.1, 0.5, 1.0, 3.5, and 5.0 wt%) were carried out. The synergism between wear and corrosion was also calculated and analyzed. The wear and damage mechanisms were elucidated by correlating the corrosion-wear synergism, morphologies, and material loss rates. The results indicated that the stable wear stage occurred at approximately 9–12 h, after which the corrosion current increased with the expansion of the wear area. As the halide concentration increased, the scale of damage on the wear scars gradually decreased, changing from being dominated by cracks, delaminations, and grooves to being dominated by scratches, microgrooves, and holes. There was an obvious positive synergism between wear and corrosion. The material loss was dominated by pure mechanical wear and wear enhanced by corrosion, but corrosion enhanced by wear contributed more than tangential sliding fretting corrosion. The total mass loss increased gradually in the range of 0.0–0.5 wt% and decreased in the range of 0.5–5.0 wt%. Large-scale damage enhanced by corrosivity and small-scale damage reduced by lubricity dominated the material loss at low and high concentrations, respectively.

Effects of High Oxygen Content on the Densification Behavior of 316L Stainless Steel During the Later Sintering Stage

Effects of High Oxygen Content on the Densification Behavior of 316L Stainless Steel During the Later Sintering Stage

High Cycle Fatigue Behaviour of 316L Stainless Steel Produced via Selective Laser Melting Method and Post Processed by Hot Rotary Swaging.

This paper deals with a study of additively manufactured (by the Selective Laser Melting, SLM, method) and conventionally produced AISI 316L stainless steel and their comparison. With the intention to enhance the performance of the workpieces, each material was post-processed via hot rotary swaging under a temperature of 900 °C. The samples of each particular material were analysed regarding porosity, microhardness, high cycle fatigue, and microstructure. The obtained data has shown a significant reduction in the residual porosity and the microhardness increase to 310 HV in the sample after the hot rotary swaging. Based on the acquired data, the sample produced via SLM and post-processed by hot rotary swaging featured higher fatigue resistance compared to conventionally produced samples where the stress was set to 540 MPa. The structure of the printed samples changed from the characteristic melting pools to a structure with a lower average grain size accompanied by a decrease of a high fraction of high-angle grain boundaries and higher geometrically necessary dislocation density. Specifically, the grain size decreased from the average diameters of more than 20 µm to 3.9 µm and 4.1 µm for the SLM and conventionally prepared samples, respectively. In addition, the presented research has brought in the material constants of the Hensel-Spittel formula adapted to predict the hot flow stress evolution of the studied steel with respect to its 3D printed state.

Cyclic deformation mechanism and fracture behaviour of 316L stainless steel under thermomechanical fatigue loading

Thermomechanical fatigue (TMF) behaviour of 316L is investigated based on the internal stress and microstructural characterization at various cyclic stages. Results reveal that the cyclic stress response shows initial hardening followed by cyclic softening at a high strain amplitude, while presenting continuous cyclic hardening as the strain amplitude decreases. Among these, Out-of-phase TMF always shows cyclic softening irrespective of strain amplitude. It is important to note that the hardening of back stress and friction stress contribute to the initial and subsequent cyclic hardening. In contrast, the subsequent cyclic softening is mainly dominated by the reduced friction stress. It is observed that the proliferation of dislocations at grain boundaries and the enhanced dislocation interactions within the grains are primarily responsible for the hardening of back stress and friction stress, respectively. Specifically, the cyclic softening of friction stress is attributed to the annihilated dislocations as a result of cross-slip. It is also found from the hysteresis curves that the intensity of dynamic strain ageing is related to strain amplitude, loading history and phase angle, which correlates to the occurrence of cross-slip, the diffusion rate of the solute atom, the density of point defect and the mobility of vacancies. Finally, the effect of loading conditions on fracture behaviour is demonstrated from the point view of crack sources, secondary cracks, creep cavities and oxidation damage.

Combined effect of process variables on the plastic behaviour of 316L stainless steel printed by L‐PBF

AbstractThe metal additive manufacturing (AM) is a technology that is rapidly spreading in the industrial sector with its enormous potential in making components with complex shapes and low weight, ensuring a high structural strength. However, the mechanical properties of the components depend on the printing process, and the interactions between the process variables and the final material behaviour is still not totally understood. In this work, 12 different types of tensile specimen were built by AM using the laser powder bed fusion (L‐PBF) technique; the used material is the 316L stainless steel. The specimens have the same geometry and the same process parameters in terms of layer thickness, hatch space, laser power, spot diameter, scanning speed and platform preheating temperature, while different laser scan strategies and building orientations are evaluated. The scope is to characterize the plastic behaviour of such specimens and study the differences due to distinct printing strategies. Stereo digital image correlation (stereo‐DIC) was used to evaluate the deformation state and analyse the material anisotropy. Finally, the microstructure and presence of defects were investigated through the optical microscopy (OM) and the scanning electron microscopy (SEM). The analysis shows how the plastic behaviour and the formation of defects are remarkably influenced by the laser scan strategy and by the building orientation.

Experimental investigation of structural behavior of 316L stainless steel and carbon steel slit dampers

To expand the range of applications for stainless steel in building structures, previous studies have tested the seismic resistance of structural elements and members using a variety of types of stainless steel. Steel slit dampers have been designed and installed for seismic retrofits of building structures. In this study, hysteresis behaviors of austenitic stainless steel (STS316L) and carbon steel (SS275) slit dampers were investigated and compared to demonstrate the excellent seismic performance of stainless-steel slit dampers. Monotonic and cyclic material tests for STS316L and carbon steel were conducted. STS316L had the best seismic performance, with much greater ductility, strength enhancement and cyclic hardening effect than SS275. STS316L with increased nickel (Ni) and reduced chromium (Cr) contents transformed to exhibit twinning induced plasticity (TWIP) steel after yielding under cyclic loading and thus possesses a more stable austenitic microstructure than SS275 and STS304. Loading experiments with STS316L and SS275 slit dampers were performed according to six loading protocols. The fracture shapes, stiffness, ductility, yield strength and energy dissipation capacity also were compared. STS316L dampers provided greater secondary stiffness, ultimate strength, number of cycles and energy dissipation capacity than SS275 dampers. The ultimate strength and normalized energy dissipation capacity of the STS316L specimens were on average 1.53 times and 4.84 times larger, respectively, than those of the SS275 specimens thanks to excellent ductility and strong cyclic hardening effects at the material level. This study proved that the performance of austenitic stainless steel STS316L as a seismic material and slit damper is superior to those of mild carbon steel SS275 and austenitic stainless steel STS304.

Effects of heat treatment through muffle furnace or microwave on microstructure and corrosion behavior of 316L stainless steel produced by selective laser melting

Effects of heat treatment through muffle furnace or microwave on microstructure and corrosion behavior of 316L stainless steel produced by selective laser melting

Tribological behavior of plasma-sprayed Yttria-stabilized zirconia thermal barrier coatings on 316L stainless steel under high-temperature conditions

Yttria Stabilized Zirconia (YSZ) coatings by plasma spray coating were performed to investigate the behavior of 316L Stainless Steel (SS) under high temperatures. The structural and mechanical properties of YSZ films were examined by successful scanning electron microscopy and Vickers microhardness. A tribotester determined the friction and wear properties at 500 and 1000 °C temperature conditions. The results showed that the surface hardness values of the YSZ-coated samples were significantly improved due to obtained ceramic layer compared with untreated 316L samples. Although the abrasive wear mechanism was observed in both the coated and uncoated samples, it was observed that higher temperatures produced smoother wear tracks. Also, increased wear test temperatures resulted in micro cracks and structural degradations on the surface of untreated stainless steel samples.

Corrosion behavior of 316L SS under cavitation condition in simulated seawater

PurposeThe purpose of this paper is to study the corrosion behavior of 316L stainless steel under cavitation condition in simulated seawater.Design/methodology/approachElectrochemical impedance spectroscopy and electrochemical noise analyses are used to characterize the electrochemical process during the cavitation erosion process.FindingsBecause of good corrosion resistance of this material, mechanical damage is the main cause of cavitation erosion. The alloy surface is in active dissolution state during the cavitation erosion process, and the corrosion rate is accelerated as time prolongs which is verified by electrochemical results.Originality/valueElectrochemical noise is an effective way to study the corrosion under cavitation erosion process.

The role of heat treatments on wear behaviour of 316L stainless steel produced by additive manufacturing

• 316L samples were produced by Additive Manufacturing method. • Heat treatment was applied to the samples to examine the microstructure changes. • Heat treatments were found to affect the wear behavior of the samples. • The wear rate is reduced by heat treatment at 650 °C. • Increased heat treatment temperature deteriorates wear resistance. In this study, 316L stainless steel (SS) samples were produced using Direct Laser Metal Sintering (DMLS) method with standard parameters. Specimens were heat-treated at 650, 950, and 1150 °C for 2 h following the DMLS process. Effects of the heat treatments on the properties of DMLS parts were examined by microstructure, hardness, and wear tests. Microstructural properties were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray (EDX) analysis. Hardness changes were determined by the Vickers hardness (HV) method. The results showed that the as-built microstructure of DMLS/316L SS deteriorated with the increase in heat treatment temperature. Moreover, heat treatment processes caused a decrease in hardness and wear resistance.

Strengthening Mechanisms and Strain Hardening Behavior of 316L Stainless Steel Manufactured by Laser‐Based Powder Bed Fusion

The microstructure–properties relations and strengthening mechanisms of additively manufactured 316L stainless steel are comprehensively investigated in this work. The orientation dependency and the strain hardening are studied by tensile testing of as‐built specimens fabricated by laser‐based powder bed fusion (LPBF) in different directions. The results are compared with those obtained for wrought material. The microstructure of the wrought and the LPBF materials are also comprehensively investigated. Equiaxed grains with random orientation and relatively uniform size (≈30 μm) are observed in the wrought material, where the LPBF samples show columnar grains inside as well as fine equiaxed grains in the bottom of the molten pool. A bimodal grain size distribution, higher values of geometrically necessary dislocations density (≈25–32%), and lower fractions of high‐angle grain boundaries (≈24–28%) are observed in LPBF 316L. A significant yield strength and considerable ultimate strength improvement without remarkable elongation decrease are obtained for the LPBF tensile specimens, resulting in a high strength‐elongation balance (up to 26 122 MPa%). Two‐stage strain hardening is depicted in both wrought and LPBF samples. This is successfully predicted with two‐stage Hollomon analysis. However, the LPBF samples illustrate lower strain hardening exponents in comparison with the wrought ones.

The corrosion of 316L stainless steel induced by methanocossus mariplaudis through indirect electron transfer in seawater

The effect of methanogenic archaea (Methanococcus maripaludis) on corrosion behavior of 316L stainless steel under different concentrations of organic electron donor (acetate) was investigated. The results showed that M. maripaludis can survive by utilizing 316L SS as an alternative energy source. The extracellular electron transfer from 316L SS relies on redox-active substances secreted by M. maripaludis. Corrosion of 316L SS is promoted along with decrease of acetate concentration. M. maripaludis causes severe pitting corrosion of 316L SS in the absence of acetate due to that more redox-active substances are secreted, which has little relationship with the M. maripaludis biofilm.

Indigenous Production of Porous 316L through Powder Metallurgy and Investigation of their Mechanical Properties

Nowadays, 316L stainless steel implant materials exhibit a promising position in the field of biomaterials application, especially in medical due to their higher strength compared to other ceramic base materials. Therefore, in this work, the production of 316L implant materials and examination of the mechanical characteristics were carried out. Powder Metallurgy process has been chosen to produce the implant materials due to its high advantages in demonstrating the high mechanical properties of the green sample. 316L stainless steel with zinc streate powder of three different compositions, i.e., the first of 99% 316L stainless steel and 1% zinc stearate, the second of 97% 316L stainless steel and 3% zinc streate, and the third of 95% 316L stainless steel and 5% zinc streate, were cold pressed individually at 600 MPa pressure using UTM and sintered the green samples at 1120 °C for 1 hour and 30 minutes. Sintering temperature and time were the same for all the specimens. We investigated the mechanical behaviour of 316L stainless steel implant materials of different compositions at the same temperature for the same duration of time. After that, the mechanical properties and densification of this material were investigated.